:root {
  --background-color: #2a3d50;
  --show-color1:#03a9f4;
  --show-color2:#f441a5;
}

* {
  margin: 0;
  padding: 0;
}

body {
  width: 100vw;
  height: 100vh;
  background-color: var(--background-color);
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: Shijie;
}

@font-face {
  font-family: "Shijie";
  src: url("../intro3S/汉仪正圆-45S.ttf");
}

.bt{
  font-size: 30px;
  color: #ffffff;
  background: linear-gradient(90deg,var(--show-color1),var(--show-color2));
  padding: 24px 48px;
  border-radius: 60px;
  position: relative;
  overflow: hidden;
}

.bt span{
  position: absolute;
  background-color: #ffffff;
  border-radius: 50%;
  transform:translate(-50%,-50%);
  animation: show 1s;
}

@keyframes show{
  0%{
    opacity: 0.5;
    width: 0;
    height: 0;
  }
  100%{
    opacity: 0;
    width: 300px;
    height: 300px;
  }
}